Visual Composer – Add Element not working

My site moved to a new server this week. Although I’ve been told that everything should now work as before, when I try to use the Visual Composer to create a new or edit an existing post, I can’t. I click on Add Element, a list of element types comes up, but when I click on any of them nothing happens.

I’ve tried clearing the cache and I’ve also tried using a different browser, but it’s still not working. Any ideas?